President Obama will nominate three new judges this morning to the powerful Federal Appeals Court in Washington D.C. The announcement is expected to come in the White House Rose Garden, and as NPR's Scott Horsley reports, there could be a few thorns.

SCOTT HORSLEY, BYLINE: On their face, none of the nominees is particularly controversial. Patricia Millett is a veteran appellate lawyer who worked in both the Clinton and George W. Bush administrations. Cornelia Pillard is a law professor at Georgetown, and Robert Wilkins is federal district judge who was confirmed unanimously in 2010. Millett and Pillard have both argued cases before the U.S. Supreme Court. All three nominees, like President Obama, graduated from Harvard Law School.

It's not easy, though, for anyone to win confirmation to the D.C. Circuit Court of Appeals, second only to the Supreme Court in its national influence. By filling three vacancies all at once, Obama could shift that court's relatively conservative political balance. Of the 14 full-time and senior judges on the court now, nine were appointed by Republican presidents, only five by Democrats.

With today's high-profile announcement, Obama is effectively challenging Senate Republicans to confirm his picks or risk a showdown over the Senate's longstanding filibuster rules. A group of Senate Republicans, led by Iowa's Chuck Grassley, wants to simply eliminate the vacancies in Washington and shift two of the openings to courts with heavier caseloads elsewhere around the country.

Grassley said last night: It's hard to imagine any reason for three more judges in Washington, no matter who nominates them. The White House countered, though, all three vacancies were occupied with Republican support during the Bush administration. Scott Horsley, NPR News, Washington. Transcript provided by NPR, Copyright NPR.